1. Field of the Invention
The present invention is directed to a mooring system for floating structures. More particularly, the present invention is directed to a mooring system for oil tankers, oil storage vessels or similar structures useful in offshore oil drilling and production facilities.
2. Description of the Prior Art
Crude oil and related refined petroleum products have been in the past and continue to be the primary source of fuel for heating, transportation and other utilities throughout the world. The need for continuing and expanded oil production has spawned a significant increase in the number of floating offshore storage and floating offshore production and storage facilities.
Oceangoing vessels such as tankers are of obvious use in offshore hydrocarbon production and storage activity. These vessels include fluid transportation means such as a transfer hose or piping which connects the vessel to the sea bed or the shore or another vessel and through which oil is transported to and from the vessel.
In transferring oil through the fluid transportation means, it is necessary to stably anchor the vessel to the ocean floor to prohibit excessive movement in rough ocean waters. Anchoring or mooring systems often further include a provision for supporting the flexible hose or pipe. It is therefore necessary that the mooring system exhibit high degrees of both strength and resiliency in providing a stable, immovable anchor for the vessel which withstands intense stress from the inevitable oscillatory and swaying motions imparted to the floating vessel by the ocean.
Heretofore, various underwater structural arrangements have been utilized for mooring floating structures such as oil tankers. For example, U.S. Pat. No. 4,637,336 to Engelskirchen discloses an anchoring arrangement which includes an underwater chamber which is suspended under the tanker and which is surrounded by a revolving platform from which anchoring chains are radially outwardly suspended. Such suspended arrangements have a number of inherent disadvantages. First, suspended arrangements are movably attached to the floating structure at various points by flexible mooring lines. This flexible attachment arrangement may fail under the intense stress of ocean use and provides a limited degree of mooring stability. Further, the majority of all of the cooperating parts of such suspended arrangements are typically below the water line when in use and therefore may be subjected to and damaged by the ocean water. Also, suspended systems typically require costly attention by a diver or team of divers to perform maintenance and repair work.
A strong need therefore exists for a mooring system which has a high degree of strength and support and which is easily maintained and repaired.